When the average person is in an instant message conversation, he won’t exactly use proper grammar and spelling (“lol” is a very common phrase). When writing a letter of recommendation to a university, one will spell check over and over again. People will talk differently under different conditions, and this surely shows it.
In an informal setting, such as instant messaging as I mentioned above, one needs to communicate quickly. Shortcuts for various words and phrases commonly overcome the need for correct spelling and grammar.
For formal communications, like when writing a letter, the quality of the writing will be very important to the recipient of the letter. One will generally take care to use correct spelling and grammar in his writing.
I often find myself following these “rules”. If you decide to pick them up, you will find that you can be both social and intelligent when communicating with others. if everyone follows my advice, we might have a better Internet (another piece of random advice).